The objective of this study is a definition of a relationship of bile acids or their metabolites to the etiology of large bowel cancer. This project will continue an investigation of the effects of diet on the quantity and nature of bile acids in the enterohepatic circulation of the rat by analyses of small aliquots of rat bile obtained at regular intervals. Identification and quantitation of bile acids will be affected by recently improved methods involving enzymatic assay, high pressure liquid chromatography, glass capillary-gas chromatography, and glass capillary gas chromatography-mass spectrometry coupled with an on-line computer.